Bobbin case holder for sewing machines



May 7, 1968 BONO 3,381,642

BOBBIN CASE HOLDER FOR SEWING MACHINES Filed July 27, 1965 INVENTOR LUIGI BONO ATTORNEYS United States Patent 3,381,642 BOBBIN CASE HOLDER FOR SEWING MACHINES Luigi Bono, Pavia, Italy, assignor to Necchi Societal per Azioni, Pavia, Italy Filed July 27, 1965, Ser. No. 475,216 Claims priority, application Italy, July 31, 1964,

Patent 740,311 1 Claim. (Cl. 112229) ABSTRACT OF THE DISCLOSURE A bobbin case holder for sewing machines comprising an improved tensioning device for the lower thread, said device comprising an arcuate clamping member of varying radius fitted along the external cylindrical wall of the bobbin holder for clamping the lower thread against said wall, and a resiliently flexible arcuate leaf spring fitted on said wall over said clamping member, said leaf spring being circumferentially displaceable along the extent of said clamping member.

The present invention relates to an improved bobbin case holder for lock-stitching sewing machines, the improvement residing in that said holder is provided with an improved means to adjustably tension the thread which is drawn from said holder. Specifically, the thread whose tension is adjusted is the lower thread of the sewing machine.

Adjustable tensioning holders are already known wherein the thread tension adjustment is realized through a very gradual variation and wherein the degree of tension is variable is measured amounts. These known holders are distinct from still earlier devices which employed a pressure spring and an elastic lamination which was placed on the external cylindrical Wall of the bobbin case.

A major object of this invention is to provide a tension adjustable holder device which constitutes an improvement over the heretofore known devices as regards simplicity of construction, efliciency in operation, low cost, and reduction in size of the essential elements.

The above and other objects of this invention will become readily apparent from the following detailed description of a preferred embodiment, which description is referred to the appended drawing, in which:

FIGURE 1 is an enlarged perspective view of the bobbin case holder with the tension regulating elements detached from the holder body; and,

FIGURE 2 is a top plan sectional view showing all the elements in assembled condition.

The bobbin case holder is denoted and is adapted to be applied to a hook (not shown) of the type having an open race. The holder 10 is comprised of a cylindrical wall 11 which is closed at one end by a bottom wall 12 which, in turn, is provided with circular openings 13. A hollow pin 14 extends upwardly and rigidly from the bottom 12 coaxially with the'wall 11 and substantially for the full height of said wall. Pin 14 is adapted to have the thread bobbin (not shown) mounted thereon in a known manner within the chamber defined by wall 11. l

Along the outer surface of wall 11 and intermediate its ends there is provided a guide ring 15-, said ring having the shape of a cylindrical crown andbeing interrupted for a circumferential portion thereof, in accordance with known practice, and said ring having an axis which is eccentric relative to the axis of pin 14, but which is coincident with the axis of the sewing machine hook carrying shaft.

The guide ring 15 is provided on its lower surface with a crown 16 of plastic material which is for the ice purpose of reducing friction between the ring 15 and the.

race of the hook.

On the portion of wall 11 which extends above ring 15 there is provided a U-shaped recess 17 in a flange 36 on the sewing machine in order to fix the position of the bobbin case holder 10 relative to said machine.

In the vicinity of recess 17 a short circumferential portion of the upper end of wall 11 is joined to ring 15 by means of a projection 18 which is provided so as to facilitate the. conveyance of the stretch of loop of the upper thread which laps the upper part of the bobbin case holder and of the bobbin.

The lower thread tensioning means comprises a resilient leaf element 19 and a tension regulating ring segment 20. The leaf element 19 has an overall arcuate contour and is constituted by two coextensive arms 21 and 22 each of which conforms to an arcuate contour of different radius, said arcuate contours meeting along axis 23. The radius of curvature of arm 21 conforms to that of wall 11 so that arm 21 fits flush against the outer surface of wall 11. Arm 22, on the other hand, has a smaller radius of curvature than arm 21, and further, its center of curvature does not coincide with the axis of wall 11, so that, when element 19' is assembled on holder 10, arm 22 remains detached from wall 11 to a progressively increasing extent as the distance from axis 23 increases. As is seen in FIGURE 2, arm 22 constitutes a thread contact portion of element 19.

Leaf element 19 is provided with a hole 24 at one end of arm 21. This hole fits closely around pin 25 Which fixedly extends from wall 11 and this engagement prevents any circumferential shifting of element 19 relative to holder 10'.

The outer end of arm 22 is reduced in height relative to the remainder of the element 19' so as to compensate for the thickness of flange 36 and to thereby avoid interference therewith when element 19 is assembled on the holder 10.

The tension regulating ring segment 20 is constituted by a band of material wihch is bent along a circular arc and defines an arcuate extent of substantially greater than degrees. The radius of the inner surface of ring segment 20 is equal to the radius of curvature of the outer surface of wall 11.

Ring segment 20 includes an end portion 26 whose height or vertical width is reduced relative to the height of the remainder of the ring segment by an amount to permit portion 26 to fit against wall 11 without being obstructed by flange 36. The terminal portion 27 of ring portion 26 is radially inwardly bent as is most clearly seen in FIGURE 2.

Ring segment 20 includes two identical elongate guide slots 28 and 29 through which extend, respectively, the pins or stud elements 25 and 30 when the member 20 is assembled on the holder 10. Pins 25 and 30 are both rigidly fixed on wall 11 and extend generally radially therefrom. Ring segment 20 is, therefore, circumferentially slidable relative to wall 11 to an extent equal to the arcuate length of the slots 28 and 29. Ring segment 20 is provided with a roughened outer surface such as knurling at 31 in order to facilitate gripping by a person for the purpose of circumferentially shifting segment 20 relative to holder 10.

With specific reference to FIGURE 2 wherein all the parts are shown in assembled condition, it is seen that resilient leaf 19 is fitted against wall 11 with pin 25 extending through hole 24 and that ring segment 20 is fitted with a portion thereof over resilient leaf 19 and with pins 25 and 30' extending through slots 28 and 29. Since ring segment extends around wall 11 for an arcuate extent of greater than 180 degrees and since its terminal portion 27 is inwardly bent, it securely grips itself onto the cylindrical wall 11 while undergoing a slightoutward elastic deformation or arching in the region adjacent to terminal portion 27, and said terminal portion 27 thereby resiliently presses inwardly against the arm 22 of leaf 19.

The thread 32 of the bobbin is led from the interior of the bobbin case holder 10, through slot 33 in said holder wall 11, and then circumferentially between the outer surface of wall 11 and the inner surface of arm 22 of leaf 19, and finally the thread is engaged with the thread guiding hook 34. It is seen, therefore, that a braking force is exerted on thread 32 by its being pressed between arm 22 and wall 11. By circumferentially shifting ring member 20 relative to wall 11, terminal portion 27 is made to press inwardly against ditferent locations on arm 22 and thereby the amount of braking force or tension against the thread is varied in accordance with the location of terminal portion 27 relative to arm 22.

In order to establish determinable tension settings for the thread, pin may be used as an index point and reference markings 35 may be provided on ring member 20 above slot 28 so that by aligning respective ones of said markings with pin 25 the tension on the thread can be varied according to fixed settings.

It is, therefore, seen from the above that a simple, efficient, and economical adjustable tensioning means is provided for adjusting the tension in lower thread 32.

It is to be understood that the above descn'bed specific embodiment represents only one possible realization of the present inventive concept and that all obvious modifications thereof are intended to be within the scope of the following claim.

What is claimed is:

1. A bobbin case holder for a sewing machine, comprising a cylindrical wall adapted to receive a thread bobbin therein, said wall having a radial opening for the 4 passage of thread therethrough, an adjustable thread tensioning means comprising a resilient leaf element extending along the outer side of said wall, a portion of said leaf element extending along an arc of smaller radius than that of said wall whereby said leaf element is spaced from said wall along the arcuate extent between the ends of said leaf element portion, said tensioning means further comprising a band of resilient material circumferentially embracing said wall along an arcuate extent thereof exceeding one end of said band radially overlapping said leaf element portion, said one end of said band being inwardly bent relative to the remainder of the arcuate extent of said band to form a bent-in end which radially bears against said leaf element portion, said band contacting said leaf element portion substantially only in the region of said bent-in end and being radially spaced from said leaf element portion along the remaining arcuate extent of radial overlap between said leaf element and said band, said band being circumferentially displaceable along said wall to thereby vary the point at which said bent-in end bears against said leaf element portion, wherein said leaf element comprises first and second arcuately coextensive portions, said first portion being of the same radius as said wall and lying flush thereagainst and said second portion being said are of smaller radius than said wall, said bent-in portion of said band adjusting the tension of the thread as said bent-in portion is moved over said are of said leaf element.

References Cited UNITED STATES PATENTS 974,309 11/1910 Thayer 412-2133 1,128,651 2/1915 Ashworth 112--233 2,488,052 11/ 1949 Robert 112--233 2,836,136 5 1958 Ayres 112229 3,016,032 l/1962 Bono 112-230 HERBERT F. ROSS, Primary Examiner.

PATRICK D. LAWSON, Examiner. 

